Devices for keeping two free piston machines at least temporarily in phase with eachother



Nov. 17, 1959 R. HUBER 2,91

mavrcss FOR KEEPING 'rwo FREE PISTON MACHINES AT LEAST TEMPORARILY IN PHASE WITH EACH OTHER Filed March 26, 1956 12' 1 Lj f Z5 25 i 3 a? 49 E a? 3454 3 F8 2] i 2 INVENTUR a eflffi 0" W f ATTUHNEYJ" United States Patent DEVICES FOR KEEPING TWO FREE PISTON MA- CHINES AT LEAST TEMPORARILY IN PHASE WITH EACH OTHER Robert Huber, Bellevue, France, assignor to Socit dEtudes et de Participations Eau, Gaz, Electrlclte Energie, S.A., Geneva, Switzerland, a Swiss society Application March 26, 1956, Serial No. 573,959

Claims priority, application France March 31, 1955 5 Claims. (Cl. 123-46) The present invention relates to devices for keeping at least temporarily in phase with each other two free piston machines, and in particular two free piston autogenerators, including pneumatic energy accumulators for producing the return strokes of the pistons.

The term free piston auto-generator designates a machine in which the power portion of the machine is scavenged by and fed with compressed air produced in the compressor portion of the machine, the power gases supplied by such machines being delivered at the exhaust ports of the power portion, which is connected with a receiving machine.

It is known that the free pistons of two machines of the above mentioned kind, and in particular of two free piston generators, assume, if no special precautions are taken, any relative position during their operation. In other words, such machines do not remain in fixed phase relation with respect to each other.

In order to obtain a predetermined phase ditference between two free piston machines, and in particular to cause them to work in opposed phases with respect to each other, it has already been proposed to connect together the pneumatic energy accumulators of these machines by means of a conduit which remains closed as long as these machines are in the desired phase relation to each other, but which is open, to permit a transfer of air from one of the accumulators to the other, when the phase difference tends to difier from its initial value.

In other installations, an opposed phase relation between two machines is obtained by constantly connecting together the pneumatic energy accumulators of these machines and controlling the amounts of fuel introduced respectively into the power cylinders of these machines in accordance with the pressure variations which exist between these accumulators as soon as the pistons are no longer in the desired phase relation, this control being then such that the amount of fuel fed to one of the autogenerators is increased and that fed to the other is reduced.

However it has been found that, in certain conditions of such installations, it is of interest to have the pistons of two auto-generators working in phase with each other, that is to say passing simultaneously through their respective inner dead center positions and outer dead center positions.

The object of the present invention is to provide a device which makes it possible to obtain the running of two free piston machines in phase with each other when so desired.

For this purpose, means are provided for placing the respective pneumatic energy accumulators of the two machines in communication with each other when it is desired to obtain an operation of the two machines in phase with each other, the same amounts of fuel being then fed to the power cylinders of the two machines respectively.

Other features of my invention will become apparent some specific embodiments thereof, with reference to the appended drawings in which:

Fig. 1 diagrammatically shows, in vertical section, two free piston auto-generators provided with a device according to my invention.

Fig. 2 shows another embodiment of the invention.

Fig. 3 shows still another embodiment.

The power plant illustrated by Fig. 1 includes two free piston auto-generators A and B.

Each of these auto-generators is arranged as diagrammatically illustrated on the drawing and includes two cylinders 1 and 2 in line with each other, the first one' being the power cylinder and the second one the compressor cylinder. The portion 2a of this compressor cylinder serves to compress air, whereas the portion 2b acts as a pneumatic energy accumulator. In these two cylinders are slidably fitted two free pistons, to wit a power piston 3 which cooperates with the power cylinder 1, and a compressor piston 4 which cooperates with the compressor cylinder 2. This compressor piston 4 serves to suck in and to compress air in the portion 2a of said cylinder 2. The compressed air cushion which is enclosed in the portion 2b of cylinder 2 serves to the accumulation of energy for returning the pistons in the inward direction from their outer dead center positions.

The power cylinder 1 includes an injector 5 and it is provided with an inlet port 6 and an exhaust port 7, these ports being controlled by the power piston 3.

The compartment 2a of cylinder 2 is provided with at least one air inlet valve 8 and at least one discharge valve 9 through which compressed air is transferred into an air reservoir 10 which surrounds the power cylinder 1.

Air is therefore sucked in past valve 8 when piston 34 is moving outwardly under the effect of the combustion of fuel in the power cylinder 1, and it is compressed and discharged into reservoir 10 when piston 3-4 is moving inwardly under the action of the energy stored up in the energy accumulator 2b during the preceding outward stroke.

The exhaust ports 7 of the power cylinders 1 of the two auto-generators A and B are connected, through their exhaust pipes 11, with a conduit 12 which conveys the power gases from the two generators to a receiver machine, for instance a turbine not shown on the drawing. Furthermore, the two reservoirs 10 of the two machines A and B are preferably connected together through a conduit 13.

For the sake of simplicity, each of the two auto-generators shown on Fig. 1 includes only one set of pistons 3-4 but, in actual practice, the auto-generators generally include two such sets of pistons opposed to each other and the power pistons of these two sets work in opposed directions in a common power cylinder 1. The compressor pistons work in two cylinders 2 opposed to each other and disposed on either side of the power cylinder 1, the opposed free pistons being connected together in the usual manner by synchronizing means.

In order to cause the two auto-generators of Fig. 1 to work in phase with each other, the respective pneumatic energy accumulators are connected together by means of a conduit 14 which, in the construction of Fig. 1, is constantly open. Furthermore, the amounts of fuel which are injected respectively into auto-generators A and B are adjusted so that they are always the same for the two auto-generators. Experience teaches that, in this way, the two machines A and B work in phase with each other. Even if, at the time of starting, the free pistons of the two machines are out of phase, they will be automatically restored into phase relation after some oscillations of the pistons.

The means for adjusting the amount of fuel fed to each of the auto-generators are of conventional construction and they consist, for instance, in a rack capable of rotating, with respect to each other, about their common axis, the piston and the cylinder of the pump 50 by means of which fuel is fed to injector 5. The piston of each pump 50 is reciprocated with respect to its cylinder by a lever '51 pivoted at 52 and actuated by a push rod 53 fixed to piston 4. When each of the auto-generators has its own injection pump 50, the racks 54 for adjusting these pumps are connected together. I may also provide a single injection pump for the two injectors.

Due to the communication 14 provided between the two energy accumulators 2b, it sufiices to provide a single stabilizer device for the two machines A and B.

On the construction of Fig. 1, the stabilizer device includes a slide valve 15. This slide valve is subjected to the action of the pressure existing in reservoir and fed, through a conduit 16, into a cylinder 17 where is movably fitted a piston 18, rigid with slide valve 15, and subjected to the action of a spring 19. On the other hand, slide valve is subjected to the action of a characteristic pressure of accumulators 2b. For instance, this pressure is the mean pressure existing in these accumulators and transmitted, through a calibrated conduit 20, to a cylinder 21 in which is movably mounted a piston 22, also rigid with slide valve 15. When the pressure in the reservoir increases with respect to that of the accumulators, the slide valve is moved downwardly, which causes a portion of the air contained in reservoir 10 to flow, past a valve 23 and through a conduit 24, into the accumulator 2b of the machine A, and thence, through conduit 14, into the accumulator 2b of machine B. On the contrary, if the pressure in reservoir 10 decreases with respect to that existing in the accumulators, slide valve 15 moves upwardly and connects conduit 24 with an exhaust opening 25.

In order to cause the pistons of the two machines A and B of Fig. l to work in phase with one another when the power plant is started, I may also have recourse to a device shown by Fig. 1. This device includes two rotating abutments 26 which, in the position illustrated by Fig. l, fix the free pistons 3-4 of machines A and B in their starting positions. In these positions, the pneumatic accumulators 2b of the two machines can be filled with a sutficient amount of compressed air supplied through a conduit 27 and which, in the position of the starting valve 28, is fed, through a conduit 29, into conduit 14 where this air is distributed between the two pneumatic energy accumulators 217. When it is desired to start the power plant, the handle 30 of valve 28 is moved from the position shown in solid lines to the position shown in dotted lines, which closes conduit 29 with respect to the air inlet conduit 27 and connects this last mentioned conduit with a cylinder 31 in which is movable a piston 32 the rod 33 of which is connected with a knuckle system 34 connected with levers 35 fixed on the shafts of rotating abutments 26. When, due to the infiow of air under pressure under piston 32, this piston moves in its cylinder 31 against the action of a spring 36, the knuckle system 34 is actuated and the two abutments 26 rotate in opposed directions so as to release the pistons 34 of the two machines A and B, respectively. Therefore these pistons are released simultaneously and pushed toward their inner dead position by the starting air stored up in accumulators 2b.

In the construction of Fig. l, the pistons of the two machines A and B are constantly in phase with one another. However, in some cases, it may be of interest to limit this kind of operation of the two machines to the starting periods, and possibly to some time after said periods, whereas, for other conditions of operation, the two machines would work in opposed phase relation. An embodiment of such an arrangement is illustrated by Fig. 2, whereas Fig. 3 shows still another modification.

In this Fig. 2, I have merely shown the ends of the two auto-generators A and B where are located the pneumatic energy accumulators 2b. In this construction, the two accumulators are connected together by a conduit 14 in which is inserted a valve 37 controlled by a handwheel 38 and which permits of opening or closing conduit 14. Furthermore, these two accumulators are connected together by a second conduit 39, normally closed by a slide valve 40. This slide valve is connected with a piston 41 including two portions. The face 41a of one of these portions is subjected to the action of the instantaneous pressures existing in one of the two accumulators, these pressures being transmitted through a conduit 42. The face 411) of the other portion of the piston is subjected to the action of the instantaneous pressures existing in the other accumulator, these pressures being transmitted through a conduit 43. The instantaneous pressures of the two accumulators transmitted to conduits 42 and 43 tend to move piston 41 into a position for which the slide valve 40 opens conduit 39. The portion 41 of the piston divides the inside of cylinder 44 into two chambers into one of which opens the above mentioned conduit 42. The other chamber of cylinder 44 is subjected to a pressure equal to the mean value of the pressures existing in accumulators 2b, this means pressure being supplied to said second mentioned chamber through a calibrated conduit 45 and acting upon piston 41 in the direction which tends to close slide valve 40.

Springs 4647 are disposed inside cylinder 44 on either side of the portion 41 of piston 41, whereby this piston is mounted floating in said cylinder.

The whole of these parts 40, 41, 46 and 47 constitutes an oscillating system such as described in the US.

Patent No. 2,473,204. This device keeps conduit 39 closed as the pistons of the two machines A and B work in opposed phase relation and restores this opposed phase relation by the transfer of some air from one of the pneumatic accumulators to the other one as soon as the pistons have a tendency to modify the desired opposed phase relation existing between them. However, when conduit 14 is open, the device constituted by the elements 39 to 47 is made inoperative and the pistons of the two auto-generators work in phase with one another. When valve 37 is closed, the device 39 to 47 is again brought into operation and then causes the two auto-generators to work once more in phase opposition, this phase relation being maintained as long as conduit 14 remains closed.

In a modification, I dispense with conduit 14 and its valve 37 and I provide means for locking slide valve 40 in the position which opens communication through conduit 39. Thus, as long as slide valve 40 is locked in this position, conduit 39 acts as a conduit interconnecting the two energy accumulators 2b of autogenerators A and B. Such a construction is illustrated by Fig. 3. In this construction, the locking of valve 40 in its open position is obtained by interposing, in the conduit 45 which serves to transmit the mean pressure in the accumulator to cylinder 44, a three-way cock 48 which, in its normal position, connects conduit 42, through conduit 45, with cylinder 44 and which, in its position for which slide valve 40 is to be locked in opening position, connects with the atmosphere the space of cylinder 44 into which opens conduit 45 while simultaneously closing the branch of conduit 45 which is connected with conduit 42.

By operating cock 48 so as to lock slide valve 40 in its open position, I cause the two auto-generators A and B to work in phase with each other, and by bringing cock 48 in the position for which the mean value of the pressure in the accumulators can act in cylinder 44, I cause the two auto-generators to work with a phase difierence of It should further be noted that operation of the autogenerator with their pistons in phase with one another is chiefly used during the starting period. Once the plant has been started, it is advisable to act either on valve 37 or on cock 48 to cause the two machines to work in phase opposition.

Of course, I have described a system for use in the case of two free piston machines, but a similar system might be used with a greater number of elementary free piston machines. It should also be noted that these machines might be motor-compressors, that is to say machines in which the compressor part, instead of supplying compressed air to the power part, delivers this compressed air directly to a receiver machine.

In a general manner, while I have, in the above description, disclosed what I deem to be practical and efiicient embodiments of my invention, it should be well understood that I do not wish to be limited thereto as there might be changes made in the arrangement, disposition and form of the parts without departing from the principle of the present invention as comprehended within the scope of the accompanying claims.

What I claim is:

1. For use in connection with two free piston machines, each of said machines comprising a power cylinder and a compressor cylinder n'gid with each other, a power piston and a compressor piston rigid with each other, said two pistons fitting slidably in said two cylinders respectively, the space between one end of said compressor cylinder and said compressor piston forming a pneumatic energy accumulator for returning said pistons inwardly from their outer dead center positions, a device for keeping said two machines at least temporarily in phase with each other which comprises, in combination, means for placing the respective energy accumulator spaces of said two machines continuously in communication with each other, and means for feeding the same amounts of fuel to the respective power cylinders of said two machines every time the respective pistons are close to their inner dead center positions.

2. In combination, two free piston machines, each of said machines comprising on the one hand a power cylinder and a compressor cylinder rigid with each other and on the other hand a power piston and a compressor piston rigid with each other, said two pistons fitting slidably in said two cylinders respectively, the space between one end of said compressor cylinder and said compressor piston forming a pneumatic energy accumulator for returning said pistons inwardly from their outer dead center positions, means for feeding the same amounts of fuel to the respective power cylinders of said two machines every time the respective pistons are close to their inner dead center positions, a device interposed between the respective energy accumulator spaces of said two machines for maintaining a relation between the respective pressures in said accumulator spaces such as to cause said two machines to work in phase opposition with respect to each other, and manual control means for placing said respective accumulator spaces continuously in communication with each other and thereby making said device inoperative.

3. A combination according to claim 2 in which said last mentioned means include a conduit interposed between said accumulator spaces in parallel with said device, and a valve in said conduit for opening or closing it at will.

4. In combination, two free piston machines, each of said machines comprising on the one hand a power cylinder and a compressor cylinder rigid with each other and on the other hand a power piston and a compressor piston rigid with each other, said two pistons fitting slidably in said two cylinders respectively, the space between one end of said compressor cylinder and said compressor piston forming a pneumatic energy accumulator for returning said pistons inwardly from their outer dead center positions, means for feeding the same amounts of fuel to the respective power cylinders of said two machines every time the respective pistons are close to their inner dead center positions, a device interposed between the respective energy accumulator spaces of said two machines for maintaining a relation between the respective pressures in said accumulator spaces such as to cause said two machines to work in phase opposition with respect to each other, said device including a conduit interposed between said respective accumulator spaces, a valve in said conduit for controlling the air flow therethrough and means responsive to the respective pressures in said accumulator spaces for automatically controlling said valve, and manual control means for locking said last mentioned means in the position for which said valve is opened.

5. A combination according to claim 4 in which said means responsive to the respective pressures in said accumulator spaces include a piston operatively connected with said valve, means for transmitting said respective pressures to one side of last mentioned piston to urge it in the direction tending to open said valve and means for transmitting the mean pressure existing in at least one of said accumulator spaces to the other side of said last mentioned piston, said manual control means being means for bringing said last mentioned side of said last mentioned piston into communication with a medium at a pressure lower than said mean pressure.

References Cited in the file of this patent UNITED STATES PATENTS 2,423,720 Mullejans et a1 July 18, 1947 2,462,745 Horgen Feb. 22, 1949 2,473,204 Huber June 14, 1949 2,605,605 Huber Aug. 5, 1952 

